Dropdown platforms especially for swimmers, divers and for tenders are known as described in the patents DE 196 02 331, U.S. Pat. No. 6,327,992, U.S. Pat. No. 5,690,045. These enable persons or material to be let down into the water or brought on board.
In the case of yachts extendable stairs from the stern or from the swim platform are known as described in U.S. Pat. No. 6,789,648 B2 or parts of the swim platform are let into the water in an arc on which carry stair elements as described in U.S. Pat. No. 7,121,226 B2.